Marine propeller



T. S. COGL|0LO. MARINE PROPELLER. APPLICATION FILED FEB. 13. 1917.

Patented Sept. 14, 1920.

'2 SHEETS-SHEET I.

WITNESSES INVENTO m ww BY W ATTORNEY T. S. COGLIOLO.

MARINE PRQPELLER.

APPLICATION FILED FEB. 13, 1911.

Patented-Sept. 14, 1920.

2 SHEETS-SHEET 2.

'2 ATTORNEY INVEN 5 wnNEssEs flj k UNITED STATES PATENT OFFICE.

IOMASO sALvAToRE-coGLIoLo, 0F GENOA/ITALY, AssIGNoR'To socIETA Esnncrzro IBAGINI, INDUSTRIALS, 0F'GENOA ITALY. Y

MARINE PROPELL ER.

To all whom it may concern Be it known that I, TOMASO SALVATORE COGLIOLO, a subject of the King of Italy, residing at Genoa, Italy, have invented certain newand useful Improvements in Marine Propellers, of which the following is a full, clear, and exact specification.

This invention relates to improvements in propellers, particularly marine propellers, and an object of the invention is to provide a propeller blade with a surface adapt ed to move in axial direction with the least possible slippage,- so as to increase the efficiency of the blade.

It is known to make propeller blades having a straight generatrix, and these propeller blades have been found to be fairly efficient. It is also known to make blade surfaces having a parabolic generatrix; and while in the use of blades having a parabolic genera-trix certain phenomena occur which do not occur in the use of a straight generatrix blade, the efliciency of the blades having a straight generatrix, as well as the efficiency of the blades having a parabolic 'generatrix, can be increased by a combination of the two surface shapes.

It is an object of the present invention to develop from a straight generatrix blade a blade having a parabolic generatrix, by

transposing parallel to the axis of the pro peller the'sine curves which constitute the lateral projections of the spiral sections which serve forbuilding'up the blade itself. This transposition of the various sine curves is proportional to the distance of corresponding points of the parabolic generatrix from those of the straight generatrix.

Owing'to the transposition described, the projection ofthe propelling surface of the blade into a vertical plane containing the axis of the propeller is reduced to a minimum withoutalteration of the pitch of the propeller taken as the basis of construction. Due to this reduction of this projected area,

'the action of the propeller will produce a slight component in transversal direction only, and the entire, or approximately entire, power applied to the propeller shaft will be consumed in the long1tudinal ad- Vance movement'of the propeller in direc tion of its axis.

The formation of the improved propeller surface from an ordinary straight generatrix propeller is illustrated in the accoinpanying drawing, 'wherein' Figure 1 is a front elevation, diagrammatically shown, of a straight generatrix propeller blade; I

Fig. 2 is a side'elevation, also-diagrammatically shown, of the same straight generatrix propeller blade; v I

Fig. 3, corresponding to Fig. .1, shows diagrammatically a front elevation of the same propellerpblade, to illustrate the fact that the transformedpropeller blade has'the same diameter and pitch as the original propeller blade; V I

Fig. 4 shows diagram atically the actually transformed prope ler blade-having a parabolic generatrix, and

Fig. 5 is a side View of the propeller on a I reduced scale.

The shape of the edges of the propeller blade, as indicated at $21. and Se, may be found in the ordinary way as aharmon-ic curve composed of portions of a spiral the equation of which is known. The radius ofare determined and are indicated at On to 6%, I

06 to6e, and 0 to 7 respectively.

The sectional lines 1, 1u,.1e or etc., appearing as circular arcs in front elevation must appear as sine curves inside projection of the propeller blade. All of these sine curves corresponding to the 'common center of the ci rcular sectional lines have a common-point of intersection with the axis of the propeller, this common point 'of intersection with this axis being indicated at -A in Fig. 2. The sine curves, furthermore, all have the same periodicity, the apices of-the' curves being located in the generatrix G, which is a side. elevation of the straight line generatrix G shown in Fig. 1. The distance of the common point of intersection A of the sine curves with the Specification of Lett ers Patent. Patented Sept, 1 4, 192(}, i

' Application filed February 13, 1917. Serial No. 148,467.

eneratrix G is assumed by .experience to geously o'ne-fourth'of the pitch of the propeller, and is indicated as such in Fig. 2 of the drawings. p

The points 0 to "Z of Fig. 1 then being projected horizontally to the generatrix thus located with respect to the point of intersection A, define the apices of the sine curves, which then can be drawn through these projections 0 to? in Fig. 2 and through the common point of intersection A. To define, then, the shape of the. edges Su and Se of the propeller blade in side elevation, it is merely" necessary to project horizontally the points of intersection of the curves Su and Se with the circular arcs of Fig. 1 to the corresponding sine curves De, la, 2a, etc.,and to connect these projected points as shown in Fig. 2, so as to define the-edgesSu and Se. The construction of propeller blades haviswell known in the art, and is repeated here merely for the purpose of facilitating the description of the development of-the blade surface having a parabolic generatrix from the blade surface having a straight generatrix having the same pitch and the same radius, but having a considerably reduced area of longitudinal projection.

For this purpose the front elevation of the blade is constructed'as shown in Fig. 1,

Fig. 3 being identical therewith. The def-.

ormation of the straight generatrix blade into a parabolic generatrix bladewith reduced projection is then accomplished by first drawing the arabolic generatrix iridicated at Gd in ig. 4. This may be a parabola intersecting the straight generatrix at the end point 7 and having a perimeter which is in a certain predetermined re lation to the radius of the blade. In the exampleillustrated, the perimeter of the parabola is given as about one-third of the radius, or .328 R.- The sine curves drawn in Fig. 2 through the straight generatrix, in which the apices are located at 0, 1, 2, etc., are then transposed to have their apices in the parabolic generatrix Gd of Fig. 4, and

it is obviousthen that they do not have a common point of intersection with the axis of the propeller. The location of the apices '0, 1, 2, 3, 4 on the parabolic generatrix Gd the points of intersection of these sine curves of Fig. 4 with the longitudinal axis of the propeller will have the same relation to each other as thejprojections of the apex front elevation until theentire edge Su mg a straight generatrix as just described points in the generatrix Gd upon the axis of the propeller will have to each other. The

axial distances of these apices are expressed in fractions of theradius R, and if, therefore, from the point of intersection of the generatrix Gd with .the axis, as indicated at E, a distance equal to 0ne; fourth ofthe pitch is measured along the axis to the point E, the intersecting points of the various sine curves with the axis will be found by measuring the distances from E to the intersecting points with the axis equal to the rojections E'O, El, as shown in Fig. 4. The location of the apex and intersection of the curve with the axis being given, the sine curves may then be drawn in Fig. 4, and on these sine curves the points 6a, 5a,

etc., and 6e, 56, etc., may be found by projecting the corresponding points from the and Se in the side elevation is found.

The propeller blade constructed in this way, having the same front elevation as a: straight generatrix blade, the same radius, and the same pitch, has a considerable area of longitudinal projection resulting in areduction of those features which have a tendency to decrease the efiiciency of the propeller blade.

I claim:

1. A propeller, having a blade the sur- I generatrix.

2. A propeller, having a blade the su'rface of which has a parabolic generatrix, but wherein the several points of the blade surface are transposed parallel to the axis of the propeller predetermined distances, said distances being proportional to the. distances of predetermined points on a straight generatrix from corresponding points of a parabolic generatrix, which intersects the straight generatrix at the terminal points of the latter.

3. A propeller having a blade the surface of which has a parabolic generatrix transformed from a straight generatrix blade by transposing the sine curves which constitute the projections of the spiralic sectional lines of the straight generatrix blade (and which intersect the propeller axis in a common point) until the apices of said sine curves are located in the parabolic generatrix.

Intestimony whereof I affix my signature in presence of two witnesses. TOMASO SALVATORE OOGLIOLO.

Witnesses: Y

A. BORAGINO, Vrrronro (JARBoNE. 

